In some internal combustion engine applications, liquid propane injection can provide some potential benefits when used for combustion. As one example, liquid propane injection provides reduced air displacement that allows for increased air mass to enter an engine cylinder resulting in increased volumetric efficiency relative to gaseous propane injection. Furthermore, in some cases, liquid propane may be more readily available and adaptable for refueling at home, such as in rural areas. Moreover, in some cases, liquid propane may provide a cheaper alternative to gasoline.
A typical liquid injection propane fuel system for an internal combustion engine supplies liquid propane from a pressurized tank via a fuel pump to a fuel rail.
However, the inventor has recognized several potential issues with such liquid propane fuel systems. For example, liquid propane in the liquid injection propane system may be exposed to high temperatures (e.g., due to engine operation) that can increase the pressure of the liquid propane beyond a liquid-to-gas phase change pressure or critical point at which liquid propane and gaseous propane are no longer distinct. At such a pressure, gaseous propane does not enter into the fuel pump and the fuel pump is unable to pump propane to the fuel rail for injection.
In one example, the above mentioned issues may be addressed by a method for controlling fuel flow in a vehicle. The method may comprise directing a liquid fuel from a fuel tank to a fuel pump, and in response to a temperature of the fuel pump being greater than a threshold, directing at least some of the liquid fuel to an expansion section, thermally connected to the fuel pump, where the liquid fuel evaporates to a gaseous fuel to thereby cool the fuel pump.
By directing liquid propane to the expansion section, the liquid propane can go from a liquid state to a gaseous state that causes a temperature drop (e.g., 218° K) that can be thermally transferred to the fuel pump to cool the fuel pump. In other words, the propane can be used as a refrigerant to cool the fuel pump so that the liquid propane does not reach the liquid-to-gas phase change pressure. In this way, the fuel pump temperature can be controlled so as to inhibit gaseous propane from entering the fuel pump and inhibiting fuel pump operation.
It will be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description, which follows. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined by the claims that follow the detailed description. Further, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this description.